1. Field of the Invention
The present invention relates to a method for fabricating capacitors of a semiconductor device, and more particularly to a method for fabricating capacitors of a semiconductor device, which is capable of achieving an improvement in chemical thermal stability, thereby enabling high integration of semiconductor devices.
2. Description of the Prior Art
The recent high integration trend of semiconductor devices inevitably involves a reduction in cell dimension. For this reason, it is necessary to form capacitors having a large capacitance while reducing the topology. In the case of a dynamic random access memory (DRAM) device constituted by one transistor and one capacitor, it is particularly important to increase the capacitance of the capacitor. In order to achieve an increase in capacitance, various methods have been proposed which are concerned with the use of a material exhibiting a high dielectric constant, the use of a dielectric film having a small thickness and the use of a lower electrode for a capacitor having an increased surface area.
By virtue of research on the application of a thin film made of SrTiO.sub.3 or (Ba, Sr)TiO.sub.3 (BST) exhibiting a high dielectric constant to highly dense semiconductor devices, a technique has been proposed which is concerned with the use of ruthenium dioxide (RuO.sub.2) or iridium dioxide (IrO.sub.2) for oxide electrodes.
Such ruthenium oxide, which is used in accordance with the above technique, has a structure having a smooth and dense surface while involving no generation of hillocks.
In accordance with this technique, however, RuO.sub.2 reacts with oxygen during a deposition of BST carried out in a subsequent MOCVD BST process, so that it may be oxidized into gaseous RuO.sub.4 or reduced into Ru in a vacuum at a high temperature. This is because the BST deposition is carried out at a relatively high temperature in an O.sub.2 atmosphere. As a result, the surface of the resulting structure becomes rough.